1. Field of the Invention
The invention relates to a saw, more particularly to a foldable saw which requires the use of only one hand when folding or unfolding the same.
2. Description of the Related Art
Referring to FIG. 1, a conventional foldable saw is shown to comprise an elongated handle member 1, a saw blade 2, a pivot shaft 3 and a locking unit 4. The handle member 1 has opposite side walls that confine a longitudinal slit 10 therebetween. The saw blade 2 is formed as an elongated flat plate with a teethed edge 20. The saw blade 2 further has a rounded end portion 21 that is provided with a pivot hole 210 and a periphery formed with diametrically opposite first and second locking notches 211, 212. The saw blade 2 is receivable in the slit 10 of the handle member 1. The pivot shaft 3 extends through the pivot hole 210 of the saw blade 2 and engages a nut 31 to connect pivotally the saw blade 2 to the handle member 1. The locking unit 4 includes a knob which has a head portion 41 and a shaft portion 40. The shaft portion 40 has an intermediate section formed with a notch 42 and a tapered segment 43 adjacent to the notch 42, and further has a distal section formed with an annular locking groove 44. The shaft portion 40 extends through the handle member 1 and is disposed adjacent to the rounded end portion 21 of the saw blade 2. A locking spring 45 is sleeved on the shaft portion 40 and biases the locking unit 4 away from the handle member 1. A C-shaped locking ring 441 engages the locking groove 44 on the shaft portion 40 to prevent removal of the locking unit 4 from the handle member 1.
Referring to FIGS. 2 and 3, when the saw blade 2 is in a folded position, i.e. the saw blade 2 is concealed within the slit 10 of the handle member 1, the tapered segment 43 of the shaft portion 40 of the locking unit 4 engages the first locking notch 211 on the saw blade 2, thereby retaining the saw blade 2 in the folded position. When it is desired to unfold the saw blade 2, the head portion 41 of the locking unit 4 is pressed, thereby causing the tapered segment 43 of the shaft portion 40 to disengage the first locking notch 211 and cause alignment between the notch 42 on the shaft portion 40 and the first locking notch 211. At this stage, the saw blade 2 is not restricted by the locking unit 4 from rotation and can be drawn out from the slit 10 of the handle member 1. When the saw blade 2 is in an unfolded position, i.e. the saw blade 2 is extended from the handle member 1, the notch 42 on the shaft portion 40 is aligned with the second locking notch 212 on the saw blade 2. Thus, once the locking unit 4 is released from the pressed state, the locking spring 45 expands to enable the tapered segment 43 of the shaft portion 40 to engage the second locking notch 212, thereby retaining the saw blade 2 in the unfolded position. The saw can be used to cut a workpiece at this time.
Note that when the saw blade 2 is moved from the folded position to the unfolded position or vice versa, one hand of the user presses the locking unit 4, while the other hand of the user pinches the saw blade 2 so as to move the latter to the desired position. Thus, folding or unfolding of the saw inconveniences the user especially when one of his hands grasps a workpiece or a railing.